Pick up the Firestorm weapon and burn away the webbing blocking the tunnel entrance in front of you. Note that if you switch weapons, you will simply drop the Firestorm at your feet. You enter a tunnel that’s completely draped in darkness. With only a flashlight in front of you, you’ll need to navigate the darkness (it’s hard to get lost) and use the Firestorm or Incineration to burn down the inflammable obstructions, mainly just the spore pods.

Don’t worry about running out of juice on your Firestorm; there are plenty strewn about next to corpses as you venture inward. As soon as you leave the pitch black darkness of the tunnel, you run headfirst into a myriad of Husks and enemies called a Ravager and Swarmers. The Ravager boasts a rock hard armored exoskeleton that will require bigger bullets to pierce through.

With the presence of rachni confirmed, you’re now tasked with finding the nest and eradicating the source. Slog through the thick cluster of spore nodes to eventually come across an important-looking barrier. A simple Overload or a few gun shots will instantly deactivate it.

Reaper tech - Located behind some webbing located after the cave-in. Gives up 3750 credits.

In the next area, your squad mates sense that imminent danger is mere moments away -- and they’re right. Husks and other enemies start flooding out and attack. Be sure to first eliminate the barrier engine, which fortifies enemies with an additional barrier that makes them tougher to kill. Many more enemies abound, which, as your squad mates point out, indicates your ever closer proximity to the nest.

Examine the narrow passage and continue deeper into the rachni’s central chamber. Aware of your intent to destroy their nest, the rachni trap you in their impenetrable fortress of metal claw-like things. You can disable one side by targeting the Reaper node above. This drops down one side of the barricade, but you’ll have much resistance to contend with.

The goal is to keep fighting your way and disabling Reaper nodes until you can reach the core node. Now you will have to make a choice of whether to walk away from the new rachni surrogate or weaponize her for your own war against the Reapers.

Either way, you’ll gain War Assets that balance out the potential loss from the other choice.